Preparation of metal nitrates.



W. 0. S'NELLING.

PREPAHAHQN or METAL NnRAEs.

APPLICATION FILED MAYIO 19H5,

mmm Nw, 26, 191e,

INVENTOR WITNESSES WALTER O. SELLING, L'ONG ISLAND CITYLNEW- YORK.

PREPARATION OF METAAL NITRATES.

Specification of Letters Patent.

'Patentedn'om 26, 1918.

Application led May 10, 1916. Serial No. 96,583.

one of its objects to provide a rapid and economical process of producing pure metal nitrates from solutions of sulids and sulfhydrates.

Another object of my invention is to proyvide a simple and effective .system of a paratus Vfor carrying outl the above-in i-` cated process in a continuous manner. Alkaline earth metal nitrates,particularly barium nitrate and strontium nitrate, are commonly prepared by heating the corresponding sulfates with coalslack` or other carbonaceous reducing agent,.leaching the resulting ash with water tol extract the metal as sulfids and sulfhydrates, treating the leachings or black ash liquor with dilute nitric acid, concentrating by evaporation, and crystallizing out the metal nitrate. In the foregoing process, if the aqueous solution of ysulids and sulfhydrates is too concentrated, the hydrogen suld evolved on the addition of nitric acid exerts a marked reducing action upon the free nitric acid present,l converting part of it into ammonium nitrate. This reduced portion of the nitric acid is therefore wasted, and the ammonium nitrate so produced remains as an impurity in the final product unless removed by careful crystallization, and may also contaminate the mother liquor to such an extent that the full crop of barium or strontium nitrate crystals cannot be Aobtained. According to .my present invention, I fol- -low the general process outlined. above, but

I employ much stronger solutions of nitric acid and of the sulfid and sulfhydrate leachings than have heretofore been used, andi'.v prevent theharmful reduction of the nitric acid to ammonium nitrate by 'mixing the acid with the leachings -in an evacuated chamber and by applying continuous suction to the reaction chamber in order to withdraw the hydrogen sulfid as fast as it. is formed` The reaction apparatus is pref?.

erably provided with means for bringing the acid angl the sulfid solution into contact in thin sheets or films having large areas exposed-.to the reduced-pressure atmosphere, in order that the hydrogen sulfid may escape from the liquid as readily as possible.

Two forms of apparatus suitable for carrying out my processl are shown in the accompanying drawing, in which Figure 1 1s a' side view, mainly in longitudinal sec: tion, of a treating vessel having a single mixingshelf'or trough, and Fig. 2 is a side view, alsoin section, showing a tower provided with a series of mixing shelves and a corresponding numberof charging and exhaust pipes.

Referring first/to Fig. 1 of the drawing, a gas-tight vessel 1, constructed of any suitable acid-rcsisting material, is provided with an inlet pipe 2 for black ash liquor and with another inlet pipe 3 for nitric acid,

the inlet pipe 3 being attached to aflong Spray .tube 4 which is suitably perforated,

` as shown, in order to project many fine` streams of acid into the black ash liquor below. The vessel l'may be circular, vrectangular or of anyother desired form, and

is provided with a gas outlet pipe 5, whichl may be attached to a vacuum pump 20 or other suitable exhaust apparatus.

Below the spray tube 4.- is a shelf or trough 6, whichis shown as being slightly inclined away from the inlet pipe 2, but whichl may be substantially horizontal. The liquid from the trough 6 falls over a dam 7 upon a second plate or shelf 8 upon which are preferably disposed :1 series of baflles or a layer of silica pebbles or other fragmentary obstructions, such as are Ashown at 9, the functionofthese obstructions being to expose the liquid in thin lms to the reduced-pressure atmosphere as long as possibleafter reaction. Adjacent to the shelf 8 is an outlet communicating with a discharge pipe 10, .which preferably extends to 'a receiving tank located more than thirty feet below the level of the trough 8, in' .order `-that the vacuum in the vessel 1 may be maintained without preventing the free outflow of liquid. A screen 11 may beprovided to prevent any of the pebbles 9 from entering the pipe 1 The apparatus shown in Fig. 2 consists of a tower 12 supported upon standards'l, and provided with a series of .horizontal or slightly inclined shelves which correspond to the shelves (5 and 8 in Fig. l and are' sinaarly designated. The upper shelf 6 is adjacent 'to an opening in the Wall of the tou'er iv` ich communicates with the black ash liquor inlet pipe 2. The acid pipe 3, in this construction, is connected to a series of short perforated pipes 14, each of which eX- tends through the Wall of the tower above one ot the shelves t5. The shelves 6 are prowith dams 7, as in the structure shown in lig. 1, for maintaining a shallow layer ot liquid thereon, and the shelves 8 are similarly provided with dams l5 and carry silica pebbles 9 or other suitable obstructions for exposing large surfaces of the liquid, jin outlet pipe 10 is provided. as in the apparatus ot Fig. l, to receive the liquid from,

the lowest shellc 8.

Disposed above each of the shelves 8 is a gas collector 1o communicating, through a slmi't pipe 17, with a vertical pipe 18 connfcted to an exhaust pipe 1l) through which the gases liberated within the tower are dra ii'n by suitable suction apparatus.

The tito forms ot' apparatus which I have slniwn and described are similar in their operation. `When barium nitgate is to be produced, crude barium sulfate is mixed with about one-it'tli of its Weight of coal slack and heated in the usual manner, the resulting ash being bleached with ivater to prod ire the so-called black ash liquor. The black ash liquor, containing sullids and sulflijvfirars and preferably fairly concentrated, is introduced into the reaction apparatus through the pipe 2 and nitric acid, also `.Fairly concentrated, is separately introduced through the pipe 3 and the perforated tubes #i or 1d. Hydrogen sullid is evolved, partly in the mixing troughs 6, but mainly upon the shelves 8,. Where the liquid is broken up into many thin films of large area. Suction being constantly maintained through the exi haust pipe 5 or 12?,"tlie hydrogenl suld is removed from the liquid substantially as fast.

as it is formed, and the liquid issuing through the pipe 10 is therefore uncontaminated with reduction products. The liydro gen sullid gas thus collected is available for -use in a variety of chemical operations.

My process eti'ects a considerable saving both in time and expense, as compared with prior processes of the same general kind. `Not only is the product exceedingly pure, because of the rapid removal of hydrogen sultitl, but'the concentration of the solutions employed greatly lessens the evaporation nceessaryin crystallizing the nitrates.

ln order that the above-described appafetus may operate automatically Without i like.

xq'iqi' n i a f. n iv w conip is ict in scura ua) s, o1 example, oy

using an excess of either black ash liquor or acid, it is ot' course necessary that the tivo liquids be supplied in proper proportions, and special precautions are'required on ae count of the evacuation of the reaction chamber, which prevents measuring the liquids by ordinary constant-level methods and the The neccessary regulation may be acmeans of the huid-measuring" ldevicel de scribed and claimed in my 'copending aA i ication for Letters Patent, Serial No. 55,7533, filed October ll. 1915. llllieii this torni ot' device is einl'iloyed, the black ash liquor may be pumped-at a constant rate through the pipe of the present apparatus, and may actuate the metering device ol Y copending application to deliver nitric ac l tothe pipe 3 in definite and proportional quantities.

It is to be undcrsl ood that the spr-cie apparatus and process ysteps which l have shown and described may be variously modified without departing from the essentials of my invention, and therefore that no liinitations are to be imposed upon my invention except such as are indicated in the appended. claims.

l claim as my invention:

1. The process thatcomprises treating' a sultid-eontainiug liquid, under sub-atmos pheric pressure, ivith an acid capable o reduction by hydrogen sulid,

2. rl`he process that comprises treating an aqueous .solution of an alkaline earth ii'ietai sulfid with nitric acidnnder sub-atmospheric pressure.

3. The process that' comprises treatiLg aqueous solution of barium sultid and suii hydrate ivith nitric acid under sub-atmos plieric pressure.

4. T he process that comprises introducing into a mixing chamber an aqueous sulid solution and an acid capable of reduction by hydrogen sullid, and maintaining sub-ritmosw plierirpressure within the said chamber.

5. The process that comprises treating an aqueous solution containing an alkaline earth metal sullid with i'iitriciacid, disposing vthe mixture in thin sheets and maintainin sub-atmospheric pressure above the said sheets ot' liquid.

6. The process thatv comprises spraying nitric acid into a solution containing barium sultid, disposing the mixture in thin sheets, and maintaining sub-atmospheric pressure above the said sheets of liquid.

In testimony whereof, l have' hereunto subscribed my name this 4th day et May 1916.

WALTER Q. SNELLETCY. 

